问题
How can one validate an XML file using an XSD in Java? We don't know the schema in advance. I would like to be able to get the schemaLocation, download the XSD, cache it and then perform the actual validation.
The problem is, that with javax.xml.parsers.DocumentBuilder/DocumentBuilderFactory classes I can't seem to be able to get a hold of the schemaLocation in advance. What's the trick for this? Which classes should I look into?
Perhaps there's a more suitable API I can use? The whole problem is that we need to validate dynamically, without (necessarily) having the XSDs locally.
How could one get a hold of the URL of schemaLocation defined in the XSD file?
I know you can set features/attributes, but that's a different thing. I need to get the schemaLocation from the XSD first.
Please advise!
回答1:
Given that you are using Xerces (or JDK default), have you tried setting this feature to true on the factory: http://apache.org/xml/features/validation/schema. There are other features that you can play with regarding schemas: http://xerces.apache.org/xerces2-j/features.html
UPDATE 2 (for caching):
Implement a org.w3c.dom.ls.LSResourceResolver and set this on the SchemaFactory using the setResourceResolver method. This resolver would either get the schema from cache or fetch it from wherever the location refers to.
UPDATE 3:
LSResourceresolver example (which I think will be a good starting point for you):
/**
* Resolves resources from a base URL
*/
public class URLBasedResourceResolver implements LSResourceResolver {
private static final Logger log = LoggerFactory
.getLogger(URLBasedResourceResolver.class);
private final URI base;
private final Map<URI, String> nsmap;
public URLBasedResourceResolver(URL base, Map<URI, String> nsmap)
throws URISyntaxException {
super();
this.base = base.toURI();
this.nsmap = nsmap;
}
@Override
public LSInput resolveResource(String type, String namespaceURI,
String publicId, String systemId, String baseURI) {
if (log.isDebugEnabled()) {
String msg = String
.format("Resolve: type=%s, ns=%s, publicId=%s, systemId=%s, baseUri=%s.",
type, namespaceURI, publicId, systemId, baseURI);
log.debug(msg);
}
if (type.equals(XMLConstants.W3C_XML_SCHEMA_NS_URI)) {
if (namespaceURI != null) {
try {
URI ns = new URI(namespaceURI);
if (nsmap.containsKey(ns))
return new MyLSInput(base.resolve(nsmap.get(ns)));
} catch (URISyntaxException e) {
// ok
}
}
}
return null;
}
}
The implementation of MyLSInput is really boring:
class MyLSInput implements LSInput {
private final URI url;
public MyLSInput(URI url) {
super();
this.url = url;
}
@Override
public Reader getCharacterStream() {
return null;
}
@Override
public void setCharacterStream(Reader characterStream) {
}
@Override
public InputStream getByteStream() {
return null;
}
@Override
public void setByteStream(InputStream byteStream) {
}
@Override
public String getStringData() {
return null;
}
@Override
public void setStringData(String stringData) {
}
@Override
public String getSystemId() {
return url.toASCIIString();
}
@Override
public void setSystemId(String systemId) {
}
@Override
public String getPublicId() {
return null;
}
@Override
public void setPublicId(String publicId) {
}
@Override
public String getBaseURI() {
return null;
}
@Override
public void setBaseURI(String baseURI) {
}
@Override
public String getEncoding() {
return null;
}
@Override
public void setEncoding(String encoding) {
}
@Override
public boolean getCertifiedText() {
return false;
}
@Override
public void setCertifiedText(boolean certifiedText) {
}
}
来源：https://stackoverflow.com/questions/9094662/validate-an-xml-against-an-xsd-in-java-getting-a-hold-of-the-schemalocation